[RESOLVED] Calculating Time

[blaknite]

I know there's a boat load of examples of this out there, but I've confused the hell out of myself.

I have 4 timers that I run on a form from a button click. They can also get started from Form_Load if certain conditions are met. Posting just one Timer block because only the variable names and label that I display the time in change in the other 3.

    'Private Sub SoldiersTimer_Tick(sender As Object, e As EventArgs) Handles SoldiersTimer.Tick
    '    soldierstime = soldierstime - 1
    '    soldierts = TimeSpan.FromSeconds(soldierstime)
    '    SoldiersTimeLabel.Text = String.Format("{0:00}:{1:00}:{2:00}", soldierts.Hours, soldierts.Minutes, soldierts.Seconds)
    '    If SoldiersTimeLabel.Text = "00:00:00" Then
    '        SoldiersTimer.Stop()
    '    call update procedure to do some things for all accounts
    '    End If
    'End Sub

'Declarations
Dim bfdateloggedoff as Date
Dim difference, soldierts, guardsments, specialforcests, thievests as TimeSpan
Dim soldierstime, guardsmentime, specialforcestime, thievestime As Integer

My Form_Load

'get the date and time the user last logged out from the db
bfdateloggedoff = dsaccounts.Tables("Accounts").Rows(reccount).Item(11) '(default value in db until I get things rolling 1/1/2013 12:00:01 AM)

'calculate the time difference between Now() and the time the user logged out

difference = bfdateloggedoff.Subtract(Now())

'timer time in seconds to countdown = number of units * 60 seconds * total minutes it will take for 1 unit
'we need to know the beginning number the user started with before they logged out

soldierstime = dsmilitary.Tables("Military").Rows(reccount).Item(4) * 60 * 12
guardsmentime = dsmilitary.Tables("Military").Rows(reccount).Item(6) * 60 * 12
specialforcestime = dsmilitary.Tables("Military").Rows(reccount).Item(8) * 60 * 12
thievestime = dsmilitary.Tables("Military").Rows(reccount).Item(10) * 60 * 12

Here is where I am stuck. Trying to translate this from english to code:

I need to compare the value in my 4 variables (soldierstime, guardsmentime, specialforcestime, thievestime) to difference.TotalSeconds (the number of seconds elapsed since user logged off to Now())

'continue where we would have left off if we hadn't closed the program
If variable_name > difference.TotalSeconds Then
   variable_name = variable_name - difference.TotalSeconds
   'Start appropriate timer
End If

'if time expired while we were logged out, change what we need to change
If difference.TotalSeconds - variable_name <= 0 Then
   'do database stuff
End If

I dont think this is correct because on the first If difference.TotalSeconds returns a negative number based on the two dates I set, so my variable will always be bigger. I believe the second If is correct.

So maybe I need to just rewrite difference = bfdateloggedoff.Subtract(Now()) and swap the Now() with the date to fix this?

[jmcilhinney]

If you want a positive result when performing a subtraction then you must subtract the lesser from the greater. If you're talking date/time then the current value is always going to be greater than a value from the past so yes, you should reverse your operands. Also, there's no need to use the Subtract method because DateTime and TimeSpan support mathematical operators nowadays:

difference = Date.Now - bfdateloggedoff

If you don;t know which is the greater and which is the lesser for some reason then you can always just use Math.Abs on the result to ensure that you have a positive value.